1. Field of the Invention
The present invention is directed generally to analyzing the operating parameters of a steam turbine generator and, more specifically, to the simulation of data representative of the condition of the turbine generator.
2. Description of the Prior Art
Turbines or similar machines include one or more blade rows each including a plurality of radially extending blades connected to a rotating shaft member. A typical blade is of a complex design which results in multiple vibration modes. If the natural resonance of the blade in one or more of those modes should coincide with the machine's rated rotational speed, or harmonics thereof, then the blade will have a tendency to vibrate excessively about its normal position. When the amplitude of that vibration exceeds a certain level, objectionable stresses are set up in the blade. If the condition is not detected and remedied, the blade may eventually fracture resulting in an extremely costly forced outage of the machinery so that the problem may be corrected.
Monitoring of blade vibration in machines already in operation is extremely important because different pressure and temperature conditions can change a blade's vibrational modes. One widely used method which tests for excessive blade vibration uses strain gages affixed to the rotating blades. Sensor information is communicated to analyzing equipment outside the machine by means of miniature transmitters affixed to the machine's rotating shaft at various locations.
Although that arrangement provides for highly accurate results, it is limited in that only a certain number of the blades can be tested at any one time due to the limited number of transmitters that can be accommodated inside the machine. To test all of the blades thus requires that the machine be shut down each time a new group of blades is to be tested so that the sensors may be properly affixed. The cost of the transmitters, and even the batteries therefore, is abnormally high since they must be of special design to withstand the extremely hostile environment inside the turbine. The high cost of equipment, in addition to labor costs, make that testing method prohibitive for many plant operators.
To obviate such problems, another testing method utilizes permanently installed, non-contacting proximity sensors to detect blade tip movement. One example of such an apparatus is disclosed in U.S. Pat. No. 4,573,358.
In that apparatus, a plurality of sensors is equally spaced about the periphery of a blade row. Each sensor is of the type which provides an output signal as a blade passes it. Signal conditioning is provided for each sensor to convert its output signal into a corresponding narrow pulse signal. A particular blade to be monitored is entered into a blade select circuit by an operator while another circuit is provided for combining all of the sensor output pulses. That combined output signal is input into a blade vibration monitor (BVM). The BVM analyses the sensor information to determine blade vibration.
Another type of BVM is disclosed in a paper entitled Development And Application Of A Blade Vibration Monitor published in Latest Advances In Steam Turbine Design, Blading, Repairs, Assessment, And Condenser Interaction, PWR-Vol. 7, edited by D. M. Rasmussen, American Society of Mechanical Engineers, 1989 at pages 37-45. That paper demonstrates that a BVM can be developed around information derived from only two sensors per row.
Regardless of the construction of the BVM and the number of sensors producing input signals therefor, all BVM's have the characteristic of being complex and sophisticated. For that reason, the need exists for an apparatus and method for evaluating the proper operation of a BVM before it leaves the factory. Additionally, there is a need for a simple method of testing and calibrating BVM's after installation.